Bug with Storm?

Hello all.
I'm new to forge but not new to MTG
I Decided to import and test my as of yet untested Tiny Leaders deck
I cast Isochron Scepter and Imprinted Brain Freeze
A few turns later
I cast High Tide 1 spell
I cast Displacement Wave with X of 1 (2 spells)
I cast Dampen Thought (3 Spells)
I activated Isochron Scepter, Copying Brain Freeze, I CAST the copy of brain freeze, Only one Brain Freeze went on the stack. when Storm should have triggered and net me 3 Copies of Brain Freeze on top of the original copied brain freeze that Isochron Scepter made.
I tried again on a later turn to cast several spells for storm count and then activate the scepter
Because you CAST the copy the secpter creates it should be triggering storm. I can understand if the scepter just put the copy on the stack but it reads
"You may copy the exiled card, If you do you may CAST the copy without paying its mana cost."
I'm new to forge but not new to MTG
I Decided to import and test my as of yet untested Tiny Leaders deck
I cast Isochron Scepter and Imprinted Brain Freeze
A few turns later
I cast High Tide 1 spell
I cast Displacement Wave with X of 1 (2 spells)
I cast Dampen Thought (3 Spells)
I activated Isochron Scepter, Copying Brain Freeze, I CAST the copy of brain freeze, Only one Brain Freeze went on the stack. when Storm should have triggered and net me 3 Copies of Brain Freeze on top of the original copied brain freeze that Isochron Scepter made.
I tried again on a later turn to cast several spells for storm count and then activate the scepter
Because you CAST the copy the secpter creates it should be triggering storm. I can understand if the scepter just put the copy on the stack but it reads
"You may copy the exiled card, If you do you may CAST the copy without paying its mana cost."